Chapter 6

Quadrilaterals

IN THIS CHAPTER

Bullet Crossing the road to get to the other side: Parallel lines and transversals

Bullet Tracing the family tree of quadrilaterals

Bullet Plumbing the depths of parallelograms, rectangles, and rhombuses

Bullet Proving a figure is a parallelogram or other special quadrilateral

In Chapters 4 and 5, you deal with three-sided polygons: triangles. In this chapter, you check out quadrilaterals, polygons with four sides. Then, in Chapter 7, you see polygons up to a gazillion sides. Totally exciting, right?

Parallel Line Properties

Most of the quadrilaterals you’ll deal with have parallel sides, so let’s begin with some info on parallel lines.

Parallel lines with a transversal

Check out Figure 6-1, which shows three lines that kind of resemble a giant not-equal sign. The two horizontal lines are parallel, and the third line that crosses them is called a transversal. As you can see, the three lines form eight angles.

Geometry of two parallel lines and one transversal line with eight angles 1, 2, 3, 4, 5, 6, 7, 8.

FIGURE 6-1: Two parallel lines, one transversal, and eight ...

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